I quote Needham, that genius of Chinese history (but getting rid of that dastardly Wade-Giles).
This is Needham's source:
In the beginning of the Kangxi reign-period (+1673) Geng Jingzhong rebelled in Zhejiang, and Prince Giyesu led a government army south to overcome the uprising. Dai Zi as a simple commoner or private scholar joined this army, and presented a design for a rapid-fire machine-gun. Its shape was like that of a balloon-guitar. The gunpowder and lead balls were all contained within the back of the gun, which was opened and closed by means of a wheel mechanism. There were also two parts fitting into each other like male and female. If one lever was pulled the gunpowder and lead bullets fell automatically into the barrel, whereupon the other mechanism followed suit and moved all together. The flint was struck, the spark came out, and the gun fired off accordingly. After twenty-eight rounds, the magazine had to be refilled with bullets. The design was in principle similar to that of the guns of the Westerners. But the weapon was not at that time widely used, and the prototype was kept at Dai's home.
Needham's commentary:
If we look at Dai's inventions in order, we see that the first must have been some kind of quick-firing machine-gun. It was a time when people everywhere were trying to make devices of kind - for example, in Samuel Pepys' diary for 3 July 1662 we read that the attention of the Royal Society was drawn to a 'rare mechanician' who claimed to be able 'to make a pistol shooting as fast as it could be presented, and yet to be stopped at pleasure, and wherein the motion of the fire and bullet within was made to charge the piece with powder and bullet, to prime it, and to bend the cock.' But the problem was not practically resolved till +1713, when James Puckle developed his breech-loading gun with a revolving set of chambers which could fire sixty-three shots in seven minutes. Thereafter the line led straight to the multi-barrel 'pepper-box' pistols and revolving 'coffee-mill' guns of Ethan Alien (1837) and thence to the Gatling gun of the American Civil War (1862) and the Maxim gun of 1883. Chinese antecedents for Dai Zi's efforts are easy to find, for we have already described the magazine crossbow, widespread in +16th-century Ming use, as also the magazine eruptor, which may well have been common considerably earlier, indeed back to +1410 or even +1350. All the same, we should very much like to have further detalls about Dai Zi's guitarshaped machine-gun.
Thoughts? What could change if this invention was widely adopted by the Qing army?